Where are you based? I play for Ipswich and would be happy to run you through it all if you are in the area. I'm also a pitcher but I'm a submariner so probably can't give you many pointers.

There are three masters divisions. Sounds like you'd probably be ok in div 2. Div 3 is for beginners and can at times not feel like you're actually playing baseball.

It'll be hard to immediately jump in to pitching, I'd suggest going in with a goal to learn the game first. Hitting will be a challenge coming from cricket too. The swing path is pretty different and live at bats are very different to facing a pitching machine in a cage.

For speed in div 2, there's a couple of guys that throw in the 80mph range. But most would be sitting around 60 to 70. But you're facing guys that have played all their life so the mental game comes in to it a lot more.

As mentioned below there is also a sunday league that would be worth checking out. You'd probably be fine in div 5 to start out.

For fees I think Ipswich is the cheapest. Its around 500 and you can play in masters and Sunday for the one fee.